Chimps and orang-utans are well known for their ability to develop tool-using tricks and transmit these within their social groups. But because gorillas are comparatively poorly studied, it’s unclear whether they develop such “traditions”. A study now suggests they do.

Richard Byrne at the University of St Andrews, UK, and colleagues looked at how captive-bred gorillas picked apart stinging nettles to eat them. They noticed that the apes never detached the stinging leaf stalks and reduced their exposure to stings by squeezing nettles together.

“This fascinated us because, while wild gorillas in Rwanda also pick apart stinging nettles, they do so by removing stalks and folding, rather than squeezing, the nettles,” says Byrne.

You can see the difference in the video above. In the first clip a captive lowland gorilla in Port Lympne, Kent, strips nettle leaves off their stem, but doesn’t twist off the stalk. Then he rolls and scrunches the bundle. The ape tucks in the leaf tips to tidy up his bundle before eating it.

In the second clip a wild mountain gorilla from Karisoke, Rwanda, strips the leaves from the stem, twists off the sting-infested stalks that attach the leaves to the stem, and then carefully folds the bundle over her thumb, underside up so that the stinging topsides are tucked away – rather than scrunching it – and pops the tidy package into her mouth.

Byrne argues that each group developed its own tactics and spread them among themselves. “The perfect study would compare only wild gorillas or only captive ones, but when that is not possible, studies like these are valuable,” says primatologist Elizabeth Lonsdorf at the Lincoln Park Zoo in Chicago. “I think we’ve only scratched the surface of gorilla learning abilities.”

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The rate of failed pregnancies among domestic horses – 37 per cent – is far higher than that in domestic cattle – 3.6 per cent – and sheep – 7.5 per cent. and colleagues at the Institute of Animal Science in Prague, Czech Republic, decided to investigate why.

The team sent out a questionnaire to horse owners throughout the Czech Republic asking for information on mares that had recently either given birth or aborted a pregnancy. It asked for details of the mare’s age, the types of horses she was housed with, the number of foals she had given birth to in the past and the way she had been inseminated.

An intriguing pattern emerged: mares that were housed with one stallion after copulating with another were seven times more likely to abort their pregnancies than mares that were kept alone during pregnancy. No mare aborted after sharing housing with the stallion that had inseminated her.

Jealous stepfather

Bartoš argues that the results make sense in light of horses’ natural behaviour. Wild horses live in “harems” consisting of one or more mares and a stallion. A stallion can gain new mares by challenging and defeating another. If a mare becomes pregnant by one stallion but then becomes a member of another harem under another stallion, she will tend to lose the developing foal and breed with the second stallion instead, he says, because stallions often kill offspring that are not their own. “The mares are just trying to avoid wasting resources on a foal that will be killed when born,” he says.

Horse breeders could learn from the study, he thinks. They often send a high-quality mare away to mate with the best available stallion – but then house the pregnant mare with local stallions on her return, increasing the likelihood that the pregnancy will fail.

But whether horse breeders will put this finding to use is another matter. “It costs a lot to put a mare in a enclosure on her own and there is a lot of tradition in this field, so I think many people will not change their ways,” says Jose Ignacio Gonzalez, an independent horse breeder in Spain.

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Over in the US alone. Could all this thumb gymnastics be subtly changing the way we feel about numbers?

Psychologists have long known that if a specific tone is consistently played while a volunteer presses a specific key on a keypad, the tone will later be mentally replayed by the user each time that key is pressed on other keypads. With this in mind, at the University of Würzburg, Germany, wondered whether the activity of texting on a cellphone might similarly lead people to associate words or ideas with numbers.

Topolinski found that 27 German study participants rated seemingly random numbers such as 373863 and 7245346 as equally pleasant. But when a further 38 German participants were asked to dial the numbers on a cellphone before rating them, they significantly preferred 373863 – equivalent to using the predictive text function to type “friend” in German – to 7245346 – German text for “slime”.

Topolinski also found that companies are more liked if their phone number spells out a company-related word, like “flower” for a florist. This applied even if the company-related word has negative connotations – “corpse” for a mortician, for example.

Subtle manipulation

Many companies already choose phone numbers precisely because they spell out a company-related word, but Topolinski says the number-word association occurs subconsciously, offering companies an opportunity for less explicit manipulation. For instance, a betting company might choose a number that spells out the word “successful” rather than the company name.

Topolinski’s studies also suggested a way for people to protect themselves from such subconscious manipulation. While dialling the numbers on a cellphone subtly changed the way participants felt about them, the same effect was not seen when the numbers were ‘dialled’ on the number pad of a computer keyboard, where the numbers are arranged in a slightly different way.

The effect may be acquired “over several years in which hands and eyes interact over and over again with the cellphone”, he speculates. “Perhaps the effect may be disturbed by simply changing the hand with which we dial.”

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It used to be received wisdom that brain cells in adult vertebrates did not replicate, but work in recent decades has proved this wrong: numerous studies with rodents show that stimulating environments lead to the birth of brain cells. So at Trinity College in Hartford, Connecticut, wondered if a specific season that was more stimulating for an animal might see cell birth boosted.

To look into this, Dunlap and his collaborator Ana Silva at the Clemente Estable Biological Research Institute in Montevideo, Uruguay, experimented with the electric knifefish (). This fish uses electric signals to interact with its environment and communicate with one another.

The team worked with the fish in three environments; a natural lake in Uruguay, a group of semi-natural outdoor ponds where the fish could socialise and a series of isolation tanks in the laboratory. They collected fish both during the warm January breeding season and in late May, during the chilly post-breeding season. Once caught, all animals were treated with , a chemical that makes recently born brain cells easy to detect.

Stimulating lake

The researchers found that the density of newly born brain cells in lake fish was two to five times greater than that found in fish from either captive environment, regardless of the season.

“This was an important finding because very few studies have examined brain cell production in the field, and when they have the effects have been relatively small or ambiguous,” says Dunlap.

However, what came as a real surprise was that the effect of the season was even greater. The densities of newly formed brain cells were three to seven times greater for fish in all three populations during the breeding season than during the non-breeding season. “We think warm temperatures are enhancing brain cell production at the same time that they trigger reproduction,” says Dunlap.

Moreover, the team noted that during the breeding season, socially housed fish had more newborn brain cells than lone fish – but only in brain regions involved in electrocommunication. The researchers speculate that the knifefish are boosting brain-cell birth in these regions to help them with social signalling and so improve breeding opportunities.

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Only adult sperm whales are able dive into deep waters to hunt for squid, so who looks after the kids? Babysitting mums, that’s who.

of Dalhousie University in Nova Scotia, and colleagues tracked two populations of sperm whales in the Caribbean and Sargasso seas to see what happened when mother whales dived for food.

The Sargasso mothers formed a babysitting circle, taking it in turns to watch over other calves and go hunting themselves. The babysitters even allowed the other mums’ calves to nurse if they were hungry. The smaller Caribbean population had fewer mothers, so calves were left with a close female relative instead.

It makes sound evolutionary sense for females to help ensure the survival of their young relatives, and for mothers to babysit in return for their own calf’s protection. However, there may be another reason the practice has arisen – a group that protects each other’s infants will grow larger, making it safer for all members.

“Among sperm whales, having extra eyes in a group to look out for killer whales is in everyone’s interest since group members are not easily replaced,” says , an expert in cetacean behaviour at the University of Massachusetts, Dartmouth. “This benefit of having a larger group may also be a reason why adults readily look after one another’s young,” he says.

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